ABSTRACT

The Perdido fold belt, within US waters of the northwestern deep Gulf of Mexico, is a late Paleogene to early Neogene structural province comprising at least five large anticlinal closures. Seismic facies analysis of undeformed strata immediately basinward of the fold belt defines the sequence stratigraphy of the Jurassic (?) through Recent section. All stratigraphic interpretation is based entirely on seismic stratigraphy because of the lack of nearby wells.

The Jurassic through lower Cretaceous interval is capped by the prominent middle Cretaceous sequence boundary (MCSB). This interval is characterized by moderate to high amplitude, low frequency, laterally continuous, parallel reflections that are interpreted as a series of primarily deep-water carbonates. The highest amplitudes and greatest reflection continuity are associated with lower Cretaceous strata. The upper Cretaceous interval has similar seismic character, but with lower amplitudes and diminished continuity, possibly suggesting dilution of carbonate deposition by pelagic/hemipelagic sedimentation. The Paleocene interval is characterized by moderate to low amplitude, continuous to discontinuous reflections that thicken to the west. Subtle erosional features and rare, slightly mounded reflections suggest stacked turbidite systems and reflect the onset of major siliciclastic deposition in the northwestern Gulf of Mexico. The Eocene interval is characterized by an upward increase in seismic reflection strength, reflection continuity, and resolution. This is interpreted to reflect turbidite systems with interbedded hemipelagic sediments, the latter component becoming more dominant up-section. Oligocene to early Miocene sediments deposited between folds display tilted onlapping to flat onlapping relationships with the folds. These reflections are interpreted to represent siliciclastic turbidite systems deposited as growth and infill strata. Middle Miocene sediments continue to infill and onlap the bathymetric relief created by fold formation. Overlying the fold belt, well imaged late Miocene to Recent sediments were deposited with chaotic, trough, and mounded reflection geometries interspersed with continuous high amplitude reflections. These geometries are interpreted as an interbedded series of slides and submarine fan deposits.